In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULI...In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULINK. Theoretical analysis and simulation experiments firstly show that not only the systematical stiffness of workpiece, spindle and tools, but also the regenerated coefficient affects the compensation displacement effect. The results show that the SREC is practicable in reality to decease the spindle induced errors in many engineering applications such as hard boring through simulation and the preliminary experiment results.展开更多
The most popular hardware used for parallel depth migration is the PC-Cluster but its application is limited due to large space occupation and high power consumption. In this paper, we introduce a new hardware archite...The most popular hardware used for parallel depth migration is the PC-Cluster but its application is limited due to large space occupation and high power consumption. In this paper, we introduce a new hardware architecture, based on which the finite difference （FD） wavefield-continuation depth migration can be conducted using the Graphics Processing Unit （GPU） as a CPU coprocessor. We demonstrate the program module and three key optimization steps for implementing FD depth migration： memory, thread structure, and instruction optimizations and consider evaluation methods for the amount of optimization. 2D and 3D models are used to test depth migration on the GPU. The tested results show that the depth migration computational efficiency greatly increased using the general-purpose GPU, increasing by at least 25 times compared to the AMD 2.5 GHz CPU.展开更多
The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke＇s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal c...The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke＇s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional （B3LYP） method by 6-31＋G＊ basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interacted with thynfine by three different hydrogen bonds as N-H…O, C-H…O, O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 k J/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the inonomer, which is in agreement with experimental results.展开更多
Wavelet estimation is a common step in seismic data processing and inversion. Homomorphic wavelet estimation has long utilized as a method that uses a seismic stack section with no phase presumption. Forming a stack s...Wavelet estimation is a common step in seismic data processing and inversion. Homomorphic wavelet estimation has long utilized as a method that uses a seismic stack section with no phase presumption. Forming a stack section, normal move-out （NMO） correction must be applied on common midpoint （CMP） gathers, although it introduces NMO stretching. After stacking, residual of the NMO stretching may affect the stack section even after muting the highly stretched zone of the NMO corrected CMP gather. Presence of significant residual NMO stretching changes the spectral characteristics of data in time direction, by different degrees. Considering that in homomorphic process the wavelet is estimated based on the spectral characteristics of data, compensating for the residual NMO stretching, can improve the accuracy of the process. Here, we introduce a fast method of calculating the amount of residual NMO stretching and compensating for its effect on wavelet estimation. The proposed method needs limited prestack information like offsets and velocity function and include no prestack processing. We apply the proposed method on synthetic and real datasets and demonstrate the improvement of the estimated wavelet.展开更多
This paper discusses the temperature field distribution of piezoelectric stack with heating and thermal insulation device in cryogenic temperature environment. Firstly,the model of the piezoelectric damper is simplifi...This paper discusses the temperature field distribution of piezoelectric stack with heating and thermal insulation device in cryogenic temperature environment. Firstly,the model of the piezoelectric damper is simplified and established by using partial-differential heat conduction equation. Secondly,the two-dimensional Du Fort-Frankel finite difference scheme is used to discretize the thermal conduction equation,and the numerical solution of the transient temperature field of piezoelectric stack driven by heating film at different positions is obtained by programming iteration. Then,the cryogenic temperature cabinet is used to simulate the low temperature environment to verify the numerical analysis results of the temperature field. Finally,the finite difference results are compared with the finite results and the experimental data in steady state and transient state,respectively. Comparison shows that the results of the finite difference method are basically consistent with the finite element and the experimental results,but the calculation time is shorter. The temperature field distribution results obtained by the finite difference method can verify the thermal insulation performance of the heating system and provide data basis for the temperature control of piezoelectric stack.展开更多
Theoretical calculation of the dissociation widths of and superdislocations with different orientations and configurations have been carried out under the equilibrium condition that the total elastic interaction force...Theoretical calculation of the dissociation widths of and superdislocations with different orientations and configurations have been carried out under the equilibrium condition that the total elastic interaction force acting on partial dislocations is balanced by the fault surface tension acting in the opposite direction. The results show that the superdislocation dissociation widths depended not only on stacking fault energies and dislocation characteristics but also on elastic anisotropy, superdislocation types and dissociation modes. Under the elastic anisotropy, the dissociation width of screw superdislocation is larger than that of screw superdislocation, and the dissociation width of edged superdislocation is smaller than that of edged superdislocation with the same stacking fault energy. The dissociation widths under the twofold, threefold and fourfold dissociations are also evaluated with anisotropy. The present results help to determine the stacking fault energies and evaluate the mobility of superdislocation in TiAl.展开更多
Temperature has great influence on the stacking fault energy (SFE). Both SFE and dγ 0/dT for Fe-based alloys containing substitutional or interstitial atoms increase with increasing temperature. Based on the thermody...Temperature has great influence on the stacking fault energy (SFE). Both SFE and dγ 0/dT for Fe-based alloys containing substitutional or interstitial atoms increase with increasing temperature. Based on the thermodynamic model of SFE, the equation $\frac{{d\gamma _0 }}{{dT}} = \frac{{d\gamma ^{ch} }}{{dT}} + \frac{{d\gamma ^{se\user1{g}} }}{{dT}} + \frac{{d\gamma ^{MG} }}{{dT}}$ and those expressions for three items involved are established. The calculatedγ 0/dT is generally consistent with the experimental. The influence of chemical free energy on the temperature dependence of SFE is almost constant, and is obviously stronger than that of magnetic and segregation contributions. The magnetic transition and the segregation of alloying elements at stacking faults cause a decrease in SFE of the alloys when temperature increases; that is, dγ MG/dT<0 and dγ seg/dT<0. Meanwhile, such an influence decreases with increasing temperature, except for the dγ seg/dT} of Fe?Mn?Si alloys. With these results, the experimental phenomena that the SFE of Fe-based alloys is not zero at the thermo-dynamically equilibrated temperature (T 0) of the λ and ε phases and they are positive both atT>T 0 andT<T 0 can be reasonably explained.展开更多
To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble mediu...To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble medium. The plume water body model was forward simulated by finite difference. Seismic records of single shot show the scattered waves produced by the plume. The scattered wave energy is strong where the plume exists. Where the scattered wave energy is stronger, the minimum of travel time is always above the plume, which has no relationship with the shot's position. Seismic records of shot gathers were processed by prestack time migration. The migration section shows that the scattered waves produced by plumes can be imaged distinctly with higher accuracy. These researches laid a foundation for further study on the seismic responses produced by plumes and provided a new approach for the identification of gas hydrate.展开更多
In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density di...In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density distribution of6 Li nucleus, the no-core full configuration (NCFC) density distribution (DD), is used to obtain the real potentials in DFM calculations. The NCFC DD results are compared with the results of both gaussian shape (GS) DD and an earlier study as well as the experimental data. This comparison provides information about the similarities and differences of the models used in calculations.展开更多
文摘In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULINK. Theoretical analysis and simulation experiments firstly show that not only the systematical stiffness of workpiece, spindle and tools, but also the regenerated coefficient affects the compensation displacement effect. The results show that the SREC is practicable in reality to decease the spindle induced errors in many engineering applications such as hard boring through simulation and the preliminary experiment results.
基金supported by the National Natural Science Foundation of China (Nos. 41104083 and 40804024) Fundamental Research Funds for the Central Universities (No, 2011YYL022)
文摘The most popular hardware used for parallel depth migration is the PC-Cluster but its application is limited due to large space occupation and high power consumption. In this paper, we introduce a new hardware architecture, based on which the finite difference （FD） wavefield-continuation depth migration can be conducted using the Graphics Processing Unit （GPU） as a CPU coprocessor. We demonstrate the program module and three key optimization steps for implementing FD depth migration： memory, thread structure, and instruction optimizations and consider evaluation methods for the amount of optimization. 2D and 3D models are used to test depth migration on the GPU. The tested results show that the depth migration computational efficiency greatly increased using the general-purpose GPU, increasing by at least 25 times compared to the AMD 2.5 GHz CPU.
文摘The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke＇s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional （B3LYP） method by 6-31＋G＊ basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interacted with thynfine by three different hydrogen bonds as N-H…O, C-H…O, O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 k J/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the inonomer, which is in agreement with experimental results.
文摘Wavelet estimation is a common step in seismic data processing and inversion. Homomorphic wavelet estimation has long utilized as a method that uses a seismic stack section with no phase presumption. Forming a stack section, normal move-out （NMO） correction must be applied on common midpoint （CMP） gathers, although it introduces NMO stretching. After stacking, residual of the NMO stretching may affect the stack section even after muting the highly stretched zone of the NMO corrected CMP gather. Presence of significant residual NMO stretching changes the spectral characteristics of data in time direction, by different degrees. Considering that in homomorphic process the wavelet is estimated based on the spectral characteristics of data, compensating for the residual NMO stretching, can improve the accuracy of the process. Here, we introduce a fast method of calculating the amount of residual NMO stretching and compensating for its effect on wavelet estimation. The proposed method needs limited prestack information like offsets and velocity function and include no prestack processing. We apply the proposed method on synthetic and real datasets and demonstrate the improvement of the estimated wavelet.
文摘This paper discusses the temperature field distribution of piezoelectric stack with heating and thermal insulation device in cryogenic temperature environment. Firstly,the model of the piezoelectric damper is simplified and established by using partial-differential heat conduction equation. Secondly,the two-dimensional Du Fort-Frankel finite difference scheme is used to discretize the thermal conduction equation,and the numerical solution of the transient temperature field of piezoelectric stack driven by heating film at different positions is obtained by programming iteration. Then,the cryogenic temperature cabinet is used to simulate the low temperature environment to verify the numerical analysis results of the temperature field. Finally,the finite difference results are compared with the finite results and the experimental data in steady state and transient state,respectively. Comparison shows that the results of the finite difference method are basically consistent with the finite element and the experimental results,but the calculation time is shorter. The temperature field distribution results obtained by the finite difference method can verify the thermal insulation performance of the heating system and provide data basis for the temperature control of piezoelectric stack.
文摘Theoretical calculation of the dissociation widths of and superdislocations with different orientations and configurations have been carried out under the equilibrium condition that the total elastic interaction force acting on partial dislocations is balanced by the fault surface tension acting in the opposite direction. The results show that the superdislocation dissociation widths depended not only on stacking fault energies and dislocation characteristics but also on elastic anisotropy, superdislocation types and dissociation modes. Under the elastic anisotropy, the dissociation width of screw superdislocation is larger than that of screw superdislocation, and the dissociation width of edged superdislocation is smaller than that of edged superdislocation with the same stacking fault energy. The dissociation widths under the twofold, threefold and fourfold dissociations are also evaluated with anisotropy. The present results help to determine the stacking fault energies and evaluate the mobility of superdislocation in TiAl.
基金This work was supported by the National Natural Science Foundation of China (Grant No.59671023) the Fund for Ph. D. Program, the Ministry of Education (No. 97024835) of China and the Emerson Electric Co. USA.
文摘Temperature has great influence on the stacking fault energy (SFE). Both SFE and dγ 0/dT for Fe-based alloys containing substitutional or interstitial atoms increase with increasing temperature. Based on the thermodynamic model of SFE, the equation $\frac{{d\gamma _0 }}{{dT}} = \frac{{d\gamma ^{ch} }}{{dT}} + \frac{{d\gamma ^{se\user1{g}} }}{{dT}} + \frac{{d\gamma ^{MG} }}{{dT}}$ and those expressions for three items involved are established. The calculatedγ 0/dT is generally consistent with the experimental. The influence of chemical free energy on the temperature dependence of SFE is almost constant, and is obviously stronger than that of magnetic and segregation contributions. The magnetic transition and the segregation of alloying elements at stacking faults cause a decrease in SFE of the alloys when temperature increases; that is, dγ MG/dT<0 and dγ seg/dT<0. Meanwhile, such an influence decreases with increasing temperature, except for the dγ seg/dT} of Fe?Mn?Si alloys. With these results, the experimental phenomena that the SFE of Fe-based alloys is not zero at the thermo-dynamically equilibrated temperature (T 0) of the λ and ε phases and they are positive both atT>T 0 andT<T 0 can be reasonably explained.
基金supported by National Basic Research Program of China(Grant No. 2009CB219505)Program for Science and Technology Development of Zhanjiang (Grant No. 2011C3107006)the Talents Introduction Special Project of Guangdong Ocean University (Grant No. 0812182)
文摘To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble medium. The plume water body model was forward simulated by finite difference. Seismic records of single shot show the scattered waves produced by the plume. The scattered wave energy is strong where the plume exists. Where the scattered wave energy is stronger, the minimum of travel time is always above the plume, which has no relationship with the shot's position. Seismic records of shot gathers were processed by prestack time migration. The migration section shows that the scattered waves produced by plumes can be imaged distinctly with higher accuracy. These researches laid a foundation for further study on the seismic responses produced by plumes and provided a new approach for the identification of gas hydrate.
文摘In the present paper, the elastic scattering of6 Li + 209 Bi system is reanalyzed by using the double folding model (DFM) at energies near the Coulomb barrier (ELab=29.9 and 32.8 MeV). With this goal, a new density distribution of6 Li nucleus, the no-core full configuration (NCFC) density distribution (DD), is used to obtain the real potentials in DFM calculations. The NCFC DD results are compared with the results of both gaussian shape (GS) DD and an earlier study as well as the experimental data. This comparison provides information about the similarities and differences of the models used in calculations.
